JPH0130229B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a device for scanning a recording track of a record carrier by a radiation beam obtained from a radiation source, in particular for scanning a video and/or audio recording surface of a rotating reflective video or audio disk. The present invention relates to an optical scanning device that scans a recording track with a light beam.

Optical scanning devices of this type for use in video disc players are known. Magazine "Philips"
Such an optical scanning device is described in a series of articles on the Philips VLP Video Disk System, Vol. 33, No. 7, 1973.

In this conventional optical scanning device, a laser beam emitted from a laser light source is focused by an objective lens to project a spot onto a disk.
The laser light source, objective lens, and photodetector are each supported by separate housings, with the reflected beam from the disk being incident on the photodetector. In order to accurately project the beam spot onto the recording track and to detect the reflected beam effectively, these optical elements must be precisely positioned, using special measurement or inspection equipment. It is necessary to adjust these optical elements to each other very precisely. Therefore, the manufacturing thereof is extremely troublesome and time-consuming, and maintenance and repair are also extremely difficult. On the other hand, in order to facilitate this adjustment work, it is preferable to make the optical axis of the device movable relative to the objective lens, but this would require the objective lens to have a large aperture. At the same time, the aberration correction must be performed over a wide range, and the conditions imposed on the design are also disadvantageous.

Furthermore, in this conventional optical scanning device,
In order to correct the radial positional deviation between the beam spot and the information track of the disc-shaped record, that is, the tracking error, the tracking mirror installed in the optical path is oscillated. When moving the objective lens, the light incident on the objective lens becomes oblique with respect to the optical axis, which has the disadvantage that the conditions imposed on the aberration correction of the objective lens become even stricter.

The object of the present invention is to eliminate the above-mentioned drawbacks and to make it possible to easily and accurately position and adjust the various optical elements without the use of special measuring devices, while also satisfying the conditions imposed on the objective lens. It is an object of the present invention to provide an optical scanning device that can be relaxed.

The present invention scans the recording track of a rotating reflective optical information record with a beam of radiation,
a radiation source for generating a radiation beam for scanning, a lens system for converging the radiation beam into a spot, and a reflecting radiation beam for receiving the reflected radiation beam modulated with information and converting it into an electrical signal. photoelectric detection means for being sensitive to the modulated radiation beam returned and converting the modulated radiation beam into an electrical signal, and for correcting focusing errors occurring during each revolution of the optical information record. a first drive means for moving the lens system at high speed in the direction of its optical axis; and a first drive means for supporting the lens system so as to be movable at high speed for focusing control.
and a second driving means for moving the lens system in the radial direction at high speed so as to compensate for tracking errors, which are deviations in the radial position of the recording track that occur during each rotation of the optical information record. An optical scanning device comprising an electro-optical pickup unit, wherein the radiation source, the lens system and the photoelectric detection means, as well as additional optical and electrical elements provided in the optical path of the radiation beam, are all arranged on a holding member. In this pick-up unit, the radiation beam always travels on the optical axis, and the second driving means acts on the holding member to move the pick-up unit at high speed in order to correct tracking errors. The present invention is characterized in that a second bearing means is provided for supporting the holding member so that the pickup unit can move at high speed to correct tracking errors.

According to such an optical scanning device of the present invention, the radiation source, lens system, photoelectric detection device, and other necessary optical and electrical elements are all arranged within the holding member, so the overall structure is very compact. become. For example, the radiation source can be a small-sized, low-power radiation source (such as a laser diode) mounted on the holding member. Also, since all the optical elements are mounted on the holding member, their positioning and adjustment is very easy and accurate, and once assembled there is little need for readjustment.
Therefore, when the optical scanning device is incorporated into a player or a recorder, it is only necessary to make the necessary connections to the electrical connection means provided on the holding member, which greatly simplifies manufacturing and maintenance. Furthermore, since the radiation beam is always located on the optical axis of the lens system, the aperture of the objective lens only needs to be small, making it easy to correct aberrations.
The design of the lens system is significantly simpler and can be cheaper. For example, the diameter of a lens system, which used to be 400 microns, can be reduced to 100 microns.

The invention will be explained in detail below with reference to the drawings.

In FIG. 1, the entire optical scanning device is designated by the number 1. The optical scanning device 1 comprises a frame 2 in which the objective lens section 3 and all the parts of the device 1 that do not move together are housed. The scanning device 1 forms part of a video disc player, which is intended for playing a video disc 4 mounted on a rotating spindle 5. The video disc consists of a transparent part 6 and a protective covering part 7 (which need not be transparent), between which there is a very thin layer with video information in the form of small holes and/or protruding parts. There is a recording surface with a reflective layer 8 .
The frame 2 of the scanning device is connected to the board 9 of the video player.
It is movably attached to the top of the A motor 11 allows the frame 2 to move within the slot 10. This motor 11 drives two bevel gears 12,
The lead screw 14 is rotated via the screw 13. The bevel gear 13 has an internal nut. The recording track of the video disk 4 has a spiral shape, and consecutive portions of the spiral are located very close to each other at a distance of several microns.

A laser diode is provided inside the scanning device 1, and the part of the radiation beam emitted by this laser diode and emerging from the objective lens section is designated by the number 17 in the drawing. One of the functions of the scanning device is to focus this part of the radiation beam onto layer 8. In other words, the objective is to make the focal plane of the objective lens coincide with the record surface as much as possible during video disc performance. For this purpose, the objective lens is moved in the direction of its optical axis. In the drawing, this direction of movement is indicated by arrow number 18. Furthermore, this objective lens portion rotates (rotates) around an axis perpendicular to the plane of the drawing, and this rotational movement is represented by curved arrow number 19. This rotational movement causes the scanning spot 2 of the radiation beam 17 to
0 will always be on the recording track of the video disk. While the video disc is rotating,
The recording track oscillates transversely to the axis 22 of the spindle shaft 5. There are two reasons for this: irregularities in the course of tracks on the disk;
This is the eccentricity of the central hole 21 and the spindle shaft 5. Generally, these vibrations are referred to as "radial vibrations," whereas the vibrations caused by the radiation spot 20 are referred to as "radial tracking." The objective lens section 3 is housed in two control circuits from the viewpoint of focusing and radial tracking. These control circuits will not be described further herein.
This is because the configurations of these circuits themselves are irrelevant to the present invention.

However, for reference, information regarding this focusing and radial tracking technique can be found in the aforementioned journals.

The objective lens section 3 is equipped with all optical elements and radiation-sensitive electronic elements, which are used to detect the position of the scanning spot and to record the video and audio information contained in the layer 8. This is necessary for scanning. The objective lens section 3 and the frame 2 are equipped with an electromagnetic focusing device and a tracking device, and these devices cooperate with each other to perform electrical control to move the objective lens section back and forth in the direction of its optical axis for focusing. It performs tracking control by rotating around a pivot axis perpendicular to the optical axis. Via the multipolar connection 23, the electronic element of the objective lens part and the electrical connection with the above-mentioned electromagnetic means are connected to an electronic circuit. These electronic circuits are built into the video player and are represented by box 24 in the drawing. The connection wire 2 is connected via the multicore conductor 25 and the multipolar connection portion 26
3 to box 24. The motor 11 is connected to the box 24 via a power supply and control conductor 27 and connections 28, 29. Since it is not necessary to control the motor 11 for focusing and tracking control, the focusing-tracking device 1 moves constantly at a speed corresponding to the average pitch of the tracks on the video disk 4. It is also possible to move the focusing/tracking device 1 intermittently, and while the device 1 is stationary, tracking is performed by the rotational movement of the objective lens section 3.

FIG. 2 shows the structure of the scanning device. The frame of this scanning device includes an annular permanent magnet 30 magnetized in the axial direction, two soft iron end plates 31 and 32 arranged at both ends of the permanent magnet in the axial direction, and an opening in the center of the permanent magnet. A hollow cylindrical soft iron core 33 located within 34 is provided. An annular gap 35 is formed between the upper end plate 32 and the core 33. A cylindrical coil structure 37 is movably disposed within this gap, and this coil structure 37 is fixed to the objective lens portion 36 and disposed about the soft iron core 33 in a coaxial relationship. The coil structure 37 together with the objective lens part is also connected to a bearing bush 39 movable in the direction of its optical axis 38. This bearing bush 39, together with a bearing bush 40 fixed to the frame, forms a focusing bearing structure including a parallel guide mechanism that guides the objective lens section parallel to its optical axis direction and performs focusing. It is.

A plastic cover 41 is placed over the top of the end plate 32 and a rubber sheet 42 is attached to it.
This rubber sheet 42 has concentric folds 43, 4.
4 and is connected to an objective lens 36. Since the shape of the rubber sheet 42 is as described above, movement in the direction of the optical axis 38 and slight rotational movements are only slightly impeded.

Attaching an annular plate 45 around the coil structure 37,
This plate 45 has local notches 46 on both opposite sides (see also FIG. 3). These notches 46 form locally formed ridges 4 of the cover 41.
7, the objective lens 36 together with the bearing bush 39 is prevented from rotating around its optical axis 38 as a whole.

The objective lens section rotates around a rotation axis 48 relative to the bearing bush 39. A pivot bearing structure is provided for this purpose. This structure has 2
A real bearing pin 49 and two bearing bushes 50 are provided. In order to control the rotational movement of the objective lens section, two annular tracking coils 51 are mounted below the bottom portion 53 of the objective lens section by means of a support member 52 (see FIG. 4). A coil 51 is arranged with play around two cylindrical axially magnetized permanent magnets 54 and 55. The poles of these permanent magnets 54, 55 are at their ends. The permanent magnets are mounted with one of their like poles facing each other and the other opposite, and the ends of their other poles are mounted in a soft iron ring 56. Due to this mounting method, a radially directed magnetic field is created at the position where the same poles of the magnets 54 and 55 are adjacent to each other, so that when the coil 51 is energized, the axial direction of the cylindrical magnet is The force is applied to the objective lens section 36, and the objective lens section 36 rotates around the pin 49.
Further, the direction of rotation is determined by the direction of the current flowing through the coil 51.

A laser diode 15 is located in the center of the bottom 53.
is mounted so that the radiation beam is always directed through the optical axis 38 to the other end of the objective lens 36. A lens system consisting of a single aspherical lens 60 is placed at this end. This aspherical lens 60 is properly placed on a lens mount 62 via a screw cap 61. In addition to this lens 60, many more optical elements are provided in the objective lens section. That is, it is a mirror 66 in which a 1/4 wavelength plate 63, a Wollaston prism 64, and an aperture 65 are formed. This mirror 66 has a reflective surface 67.
is formed. Furthermore, this objective lens section is provided with an aperture plate 68 for focusing half of the radiation beam generated from the light guide 59 and two radiation-sensitive diodes 69, 70, which convert the optical beam modulation into a high-frequency video signal. It also has the function of converting into audio information and information on the position of the focal plane relative to the recording surface.

Electrical connection lines for coil 51, diodes 69, 70, and coil 37 are not shown in the drawing. However, it is preferred that the connecting wires of the coil 51 and the diodes 69, 70 lead upwardly through the wall of the bearing bush 39 in the vicinity of the bearing pin 49, thereby connecting the connecting wires to a mounting pin 71 arranged in the cover 41. be able to.

The optical element in the objective lens section 36, diodes 69, 70, and aperture plate 68 constitute a device for reading optical information, and data regarding this information is disclosed in Japanese Patent Application Laid-Open No. 1983-71155 filed by the applicant. It is stated in the specification. This specification discloses the operation of the automatic focusing mechanism of the objective lens section 36. Regarding the automatic tracking mechanism, the published patent specification (Netherlands Patent Application No. 7401470)
The system described in can be used. In this system, the information track of the record carrier is recorded by periodically oscillating it slightly, so that a signal of small amplitude is superimposed on the light beam modulation.
This superimposed signal contains position information of the scanning spot relative to the record track.

The objective lens portion of the scanning device shown in FIG. 5 is designated by the number 72. In the permanent magnet circuit, a permanent magnet 73 magnetized in the axial direction is inserted into the central opening 7 of the two shaft ends.
4 and two soft iron end plates 75, 76. A hollow soft iron core 77 is disposed within the central aperture 74. A cylindrical coil structure 78 arranged coaxially around this soft iron core 77 is fixed to the objective lens part 72, and a first annular gap 79 between the end plate 75 and the core 77 and a first annular gap 79 between the end plate 76 and the core 77 are formed. axially movable within a second annular gap 80 between the two. The focusing bearing structure is a sleeve bearing structure for guiding the objective lens part 72 in parallel, and a first bearing bush 82 is connected to the objective lens part and movable in the axial direction with respect to the bearing bush 81. Equipped with. This bearing bush 81 is fixed to the soft iron core 77 by two bearing pins 83. While these bearing pins are fixed to the soft iron core 77,
Two bearing bushes 84 fixed to the bearing bush 81 are rotatable about the pin. As described above, in this embodiment, the bearing bush 82 is fixed to the objective lens section 72 and can be moved in the axial direction within the bearing bush 81. It is of course also possible to use it as a part of the outer wall sleeve bearing structure of the objective lens section 72 itself.

The main advantage of the structure of FIG. 5 is that only a single electromagnetic system is needed to move the objective part 72 in the direction of its optical axis 85 and to rotate it around a pivot axis 86 for tracking movements. These two functions are achieved by the permanent magnet 73. Comparing this with the embodiment of FIG. 2, the mass that must be moved in the direction of the optical axis 85 can be reduced. Coil structure 78 comprises two coils 87 symmetrically arranged on each side of pivot axis 86 (see also FIG. 6). This coil 87 has both focusing and tracking functions. A mounting plate 88 (FIG. 5) to which the cylindrical soft iron core 77 is attached forms an annular gap, that is, a gap 79, 80 between each of the end plates 75, 76 and the core 77. can get. Therefore, the efficiency of the electromagnetic means for axial operation and rotation of the objective lens section 72 is high. A portion 89 of each winding of coil 87 extends into air gap 79 and another portion 90 extends into air gap 80. These coil portions 89, 90 are arranged so that they equally share the torque generated electrically around the rotation axis.

The electromagnetic force generated in portions 89, 90 of coil 87 is oriented in the axial direction. Corresponding parts of two coils 8
Focusing operation is achieved if the currents through 9, 90 are chosen such that the axial forces are in the same direction and are equal. If it is different from this, the objective lens portion rotates and a tracking operation is performed.

7 to 10 show the configuration of another example of a scanning device, in which an objective lens section 91 rotates around a rotation axis 92 parallel to these optical axes 93. Two leaf springs 9 with rotating objective lens support members 94 arranged parallel to each other.
6. Focusing bearing structure 95 and screw 97
and a locking plate 98 to connect to the frame 99 . This frame 99 includes a substrate 100 to which a support member 101 is fixed with bolts 102.

A tracking bearing structure 103 rotatably connects the objective lens section 91 to the objective lens support member 94 . This bearing structure 103 consists of four identical leaf springs 104 arranged in a criss-cross pattern with each other. One end of these springs 104 is glued to the objective lens support member 94, and the other end is glued to the objective lens part 91. do.

The electrically controllable focusing means 105 includes an axially magnetized permanent magnet 106 glued to the frame 99 , arranged concentrically with this permanent magnet, and glued to the objective lens support member 94 . Both the permanent magnet and the coil are coaxial with the objective lens part 91, and the magnet 106 has a hole 108.
is formed, and this hole 108 is for the passage of a radiation beam obtained from a radiation source (not shown).
The electrically controllable tracking means 109 comprises an assembly of two cylindrical axially magnetized permanent magnets 110 connected to the objective lens support member 94 and arranged concentrically around this assembly, the objective lens part 91, and these permanent magnets are mounted so that their like poles face each other. The axes 112 of these tracking means are spaced apart from the optical axis 93 of the objective lens 91 by a certain distance and are opposite the pivot axis 92 of the tracking bearing structure 103.

Two tabs 113 are provided on the objective lens support member 94 for fixing the two permanent magnets 110 on this support member. The two magnets have holes through which bolts 114 pass, thereby locking the magnets between tabs 113.

The coil 111 is glued to a holder soldered to the sleeve 116, and the objective lens section 91 is properly placed within the sleeve 116. A leaf spring 104 is connected to the objective lens section via this sleeve.

In this example, the radiation beam emitted from the laser diode can be guided to the objective lens section 91 via a hole 108 made in the permanent magnet 106.

[Brief explanation of drawings]

Fig. 1 is a diagram when the optical scanning device of the present invention is used in a video disc player, Fig. 2 is a cross-sectional view of an example of the optical scanning device of the present invention, and Fig. 3 is a partial cross-section of the device shown in Fig. 2. 4 is a cross-sectional view of a portion of the device shown in FIG. 2, FIG. 5 is a cross-sectional view of a modification of the device of the present invention, FIG. 6 is a perspective view of the tracking coil shown in FIG. 5, and FIG. The figure is a cross-sectional view of another example of the device of the present invention, FIG. 8 is a cross-sectional view along the line - in FIG. 7, FIG. 9 is a plan view of the device in FIG. FIG. 1... Optical scanning device, 2, 99... Frame, 3,
36, 72, 91...Objective lens section, 4...Video disk, 5...Spindle axis, 10...Slot, 1
5... Laser diode, 24... Electric circuit box, 30, 54, 55, 73, 106, 110...
Permanent magnet, 31, 32, 75, 76, 80... End plate, 33, 77... Hollow soft iron core, 35, 79... Gap, 37, 51, 87, 78, 89, 90, 10
7,111...Coil, 39,40,81,84...
Bearing bush, 38, 85, 93...optical axis,
48, 86, 92...Rotation axis, 60...Aspherical lens, 63...1/4 wavelength plate, 64...Wollastone prism, 66...Mirror, 69,70...Radiation-sensitive element, 96,104...Leaf spring , 100...
Substrate, 103...Tracking bearing structure, 1
12...Tracking axis.

Claims (1)

[Claims] 1. A scanning device for scanning the recording track of a rotating reflective optical information record with a radiation beam, receiving the reflected radiation beam modulated with information, and converting it into an electrical signal. A radiation source that generates a radiation beam, a lens system that focuses the radiation beam into a spot, and a photovoltaic system that is sensitive to the modulated radiation beam that is reflected back and converts the modulated radiation beam into an electrical signal. detection means; first drive means for moving said lens system at high speed in the direction of its optical axis so as to correct focusing errors occurring during each rotation of the optical information record; and a lens for focusing control. first bearing means for supporting the system so as to be movable at high speed; and a first bearing means for supporting the system for high speed movement, and for radially moving the lens system to compensate for tracking errors, which are deviations in the radial position of the recording tracks that occur during each rotation of the optical information record. and a second drive means for moving at high speed, the radiation source, the lens system and the photoelectric detection means, as well as additional optical and electrical elements provided in the optical path of the radiation beam, all mounted on a holding member. arranged to form an electro-optical pick-up unit, in which the radiation beam always travels on the optical axis, and the second driving means acts on the holding member to track the pick-up unit. A second bearing means is provided for supporting the holding member so that the holding member can be moved at high speed to correct errors and the pick-up unit can be moved at high speed to correct tracking errors. optical scanning device.